 ; head
 (defn head-1
   "head <list> # returns the first item from the <list>"
-  {:yb/cat #{:util}}
+  {:yb/cat #{:util :collection}}
   [cmd-args]
   (head 1 cmd-args))
 
 (defn head-n
   "head <n> <list> # return the first <n> items from the <list>"
-  {:yb/cat #{:util}}
+  {:yb/cat #{:util :collection}}
   [{[_ n] :match :as cmd-args}]
   (head (read-string n) cmd-args))
 

; letters
(defn letters
  "letters <string> # turn <string> into a sequence of individual letters"
  {:yb/cat #{:util}}
  [{args :args}]
  (map str (seq args)))


; unwords
(defn unwords
  "unwords <list> # join <list> with a single space"
  {:yb/cat #{:util :collection}}
  [{args :args opts :opts}]
  (if (nil? opts)
    args ; no collection, return the value as-is
